1. Field of the Invention
The invention herein relates to valves and connectors, such as those use in medical liquid flow applications such as intravenous (IV) administration of medications. More particularly it relates to needleless valves for such applications.
2. Description of the Prior Art
There are many instances, particularly in the medical field, where quantities of liquid must be moved from a source of the liquid to a liquid conduit system under restricted and usually sterile conditions. A principal example is the administration of medication or other liquids to a patient intravenously. When the intravenous administration is to be conducted at periodic intervals over a extended period of time, the conventional practice is to insert a catheter into the patient's vein, usually through the patient's forearm, and leave the catheter in place with a portion extending out of the patient's arm and terminating in a valve (receiver) for periodic connection to the liquid source as required. The presence of the valve avoids the necessity of using direct injection of the patient each time the medication is to be administered, which would be both painful to the patient and also increase the risk of infection each time the skin was penetrated.
For many years, receivers of valves were constructed with a resealable membrane, such as a rubber or other elastomeric plug, stretched across the inlet end of the device, closing off the IV fluid conduit. When it was time to administer medication or other fluid, the physician or nurse would use a conventional hypodermic syringe with a sterile hypodermic needle which would penetrate the rubber plug and allow sterile injection of the fluid in the syringe directly into the liquid conduit or cannula. Upon withdrawal of the hypodermic needle, the elastic rubber plug would resile and seal itself, maintaining the sterile condition of the interior of the system.
Such practice, however, has numerous disadvantages. Repeated piercing of the plug with the hypodermic needles eventually damages the plug sufficiently that it cannot maintain the appropriate sterile seal. Further, since the valve/receiver devices are normally quite small, the plug is even smaller, often less than 1/4 inch (6 mm) in diameter. Therefore the person administering the medication had to take care in manipulating the syringe so that the hypodermic needle would pierce the rubber plug and not hit the other portions of the receiver, the patient's arm, or even the hands or arms of the person himself or herself. To take the appropriate amount of care, of course, required some period of time, thus reducing the number of patients a physician or nurse could serve in a given time period. In addition, it was not uncommon for hypodermic needles to break off in the plug during or before administration of the liquid, thus usually becoming lodged in the rubber plug and requiring the administrator to take time to remove the broken needle. Further, such breakage also commonly caused the loss of all or a portion of the medication or other liquid in the syringe and, of course, not properly administered to the patient.
Such problems were particularly common in situations where the medical personnel were required to act very rapidly, such as in emergency room and emergency medical administration settings.
The accidental piercing of the skin of the doctor or nurse raised critical problems. If such occurred before administration of the medication to the patient, the medication, or at least a portion of it, was injected into the nurse or doctor, which not only deprived the patient of the medication, but in fact might be quite harmful to the physician or nurse. If the accident occurred after administration of the fluid to the patient, the hypodermic needle could easily be contaminated by the patient's blood or other bodily fluid, thus being capable of transmitting the patient's disease to the physician or nurse. While this was a severe problem at any time, it became a truly critical problem as various highly infectious or virulent diseases became more prevalent in the population. The added presence of infectious diseases with extremely high rates of mortality among patients, such as AIDS, gave priority to development of devices which would eliminate the need for use of hypodermic needles.
In more recent years, "needleless" connectors and receptors have been developed and widely marketed. In systems using this type of device, the fluid dispenser (usually a syringe) is fitted with a blunt nozzle rather than a hypodermic needle. The blunt nozzle is designed to be received into a corresponding receiver attached to the IV line or other fluid conduit. Within the receiver is normally a hollow tubular cannula, which is a fixed member forming the extended end of the fluid conduit extending into the patient's veins. Sterility of the receivers is important so that transfer of the liquid from the syringe to the cannula and IV fluid conduit can be conducted under sterile conditions.
While the "needleless" concept has been well known and is quite simple, implementation of the concept in practice has been quite difficult. Needleless connectors have, for the most part, been designed with a hollow flexible plug which fits over the cannula and which has a self-sealing slit or similar closeable opening in its exterior end. The interior end of the plug is anchored adjacent to the downstream end of the cannula (i.e. the end leading into the IV system and the patient's arm). Since the cannula is made as a rigid elongated tube, as the nozzle of the fluid dispensing device is pushed into the receiver, it contacts that exterior end of the rubber plug and forces that end inwardly against the distal end of the cannula. The distal end of the cannula contacts the slit at the end of the plug and forces the slit open, so that the plug then becomes a sleeve as it is pushed inwardly along the outer surface of the cannula. Eventually, the distal end of the cannula, now being exposed, contacts the interior fluid transfer tube of the dispensing device as the nozzle of the dispensing device moves further into the receiver. When this connection is made, the fluid can be transferred from the syringe directly into the cannula through which it flows onto the IV system in the patient's body. Such opening of the device is commonly referred to as "activation" of the "valve."
Once the fluid is fully transferred, the nozzle of the dispensing device is withdrawn outwardly through the receiver, causing the flexible plug to resile and extend distally along the cannula until it passes the cannula end and returns to its "deactivated" position enclosing the end of the cannula with the slit again sealed. Examples of devices of this type are shown in U.S. Pat. Nos. 5,065,783 (Ogle) and 5,549,577 (Siegel et al.) and in published PCT application no. WO 93/11828 (Lopez).
While such devices have worked well for the most part, they have been found to have some serious deficiencies. One of the most important is the fact that upon deactivation and withdrawal of the nozzle of the syringe or other fluid dispensing device, the compressed plug resiles back to its original position, thus increasing its internal volume back to its deactivated volume, thus creating a partial vacuum in the cannula and attached catheter. This produces a suctioning effect which often causes the patient's venous blood to be drawn into the catheter where it remains and can clot, thus preventing flow through the catheter. When it comes time to administer the next fluid dose, the plugged catheter prevents administration of the fluid. Remedying of the problem requires that the catheter be cleaned or replaced. This, of course, is a major problem in emergency situations, whether in an emergency room or when a patient on IV suffers some sort of relapse or seizure or other critical condition and medication must be administered through the IV without delay. Even in the absence of an emergency, however, withdrawal of the device for cleaning of the catheter requires that the IV subsequently be reinserted into the patient. In ordinary situations this at least requires the time of a nurse and is a discomfort for the patient. In many cases, however, reinsertion is a problem that requires a doctor's intervention, as for instance where an new acceptable insertion site is difficult to find or the patient does not tolerate needle insertions well. Thus reinsertion presents a significant cost event for the medical team and subsequently for the patient.
Other forms of connectors in needleless couplings have been described. These may have components within the coupling intended to hold the fluid flow conduit open against the tendency of flexible sleeves attached to one or the other end of a coupled tubing to compress and close the fluid flow path. A typical example is shown in U.S. Pat. No. 4,457,749 (Bellotti et al.) in which a "spike" having a cruciform cross section is used to hold open a fluid path within the coupling as the two portions of the tubing are joined together.